UV-curable fresnel lens resin composition, fresnel lens, and back projection screen

ABSTRACT

UV-curable Fresnel lens resin compositions  1a! comprising a (meth)acrylate containing hydroxyl group and aromatic ring (A1), a urethane group-containing (meth)acrylate (A2) comprising an aromatic diol, an aromatic ring-containing monofunctional (meth)acrylate (A3), and a photopolymerization initiator (B) and  1b! comprising (A1), a mono- or di(meth)acrylate monomer (A4), and (B), further supplemented with a polyester (C1) comprising an aromatic diol and a phosphate (C2) for the formation of a Fresnel lens on a sheet or plate made of a methyl methacrylate (co)polymer; a Fresnel lens formed by UV cure of composition  1a! or  1b!; and a rear projection screen including a sheet or plate carrying said Fresnel lens. The Fresnel lens has high refractive index, antistatic properties and is satisfactory in adhesion to a sheet or plate.

FIELD OF THE INVENTION

The present invention relates to a UV-curable Fresnel lens resincomposition, a Fresnel lens, and a rear projection screen. Moreparticularly, the invention relates to a UV-curable Fresnel lens resincomposition showing good adhesion to a sheet or plate made of ahomopolymer of methyl methacrylate or a copolymer of methyl methacrylatewith one or more other acrylate or methacrylate (hereinafter referred tocollectively as methyl methacrylate (co)polymer); a Fresnel lenscomprising a resin formed by UV cure of said composition in situ on saidsheet or plate; and a rear projection screen including a sheet or platecarrying said Fresnel lens.

DESCRIPTION OF THE PRIOR ART

The Fresnel lens heretofore used for the fabrication of a rearprojection screen is manufactured typically by casting a UV-curableresin composition between a mold and a transparent resin sheet or platemade of a methyl methacrylate (co)polymer, and exposing the resincomposition to ultraviolet light, and thereby curing it.

With the recent trend toward reduced thickness of projection televisiondevices, a demand exists for resins with high refractive indices andaccordingly a variety of UV-curable resin compositions have beenproposed (e.g. Japanese Kokai Publications Hei-5-65318, Hei-5-155944,Hei-5-247156, and U.S. Pat. No. 5,453,452).

However, the proposed UV-curable resin compositions are unsatisfactoryin the adhesion to a sheet or plate made of a methyl methacrylate(co)polymer, and require a primer on the sheet or plate. Moreover, thelens obtainable from any of those UV-curable resin compositions has theproblem of static deposition of dust particles.

As compositions which can be used without the aid of a primer and yetshow improved adhesion to a sheet or plate, the following compositions 1and 2 were proposed. On the other hand, as compositions solving theabove-mentioned problem of static deposition of dust particles, thefollowing composition 3 has been proposed.

1 A composition comprising diacrylate or dimethacrylate of a lowmolecular hydrocarbon diol (e.g. EP-510754A1)

2 A composition comprising an epoxy acrylate or methacrylate(e.g.Japanese Kokai Publication Hei-5-310871)

3 A UV-curable resin composition having antistatic properties (e.g.Japanese Kokai Publications Hei-1-302201 and Hei-3-157412)

However, any of these compositions 1 to 3 has the drawback that anattempt to insure sufficiently high adhesion to a sheet or plate resultsin a reduced refractive index and/or poor scratch resistance of the lenssurface owing to embrittlement of the resin, so that it has beenimpossible to obtain a Fresnel lens meeting all the requirements ofacceptable adhesion, refractive index, and scratch resistance.

It is an object of the present invention to provide a UV-curable resincomposition capable of providing a Fresnel lens satisfactory in all theparameters of adhesion to a sheet or plate, refractive index, andscratch resistance.

It is a further object of the present invention to provide a UV-curableresin composition capable of providing a Fresnel lens further havingantistatic properties.

It is a still another object of the present invention to provide aFresnel lens having all of the above-mentioned characteristics.

It is a further object of the present invention to provide a rearprojection screen including a Fresnel lens sheet or Fresnel lens platecarrying a Fresnel lens having all of said desirable characteristics.

SUMMARY OF THE INVENTION

The above objects have been accomplished by the present invention whichprovides the following UV-curable resin compositions 1a! and 1b!;Fresnel lenses 2a! and 2b!; and rear projection screens 3a! and 3b!.

1a! UV-curable resin composition

A UV-curable Fresnel lens resin composition for use in the formation ofa Fresnel lens on a sheet or plate made of a methyl methacrylate(co)polymer, said resin composition comprising.

(A1) an acrylate or methacrylate (herein after referred to collectivelyas (meth)acrylate) containing hydroxyl group and aromatic ring;

(A2) a urethane group-containing (meth)acrylate having a moiety of anaromatic diol (a1) represented by the following general formula:##STR1## wherein Ph represents 1,4-phenylene group, R¹, R² and R³ eachrepresents hydrogen atom or methyl group, m and n each represents aninteger of 1 to 15, and (m+n) is equal to 2 to 20;

(A3) an aromatic ring-containing monofunctional (meth)acrylate; and

(B) a photopolymerization initiator.

1b! UV-curable resin composition

A UV-curable Fresnel lens resin composition for use in the formation ofa Fresnel lens on a sheet or plate made of a methyl methacrylate(co)polymer, said resin composition comprising

(A1) a (meth)acrylate containing hydroxyl group and aromatic ring;

(A4) a mono- or di(meth)acrylate monomer with a molecular eight of 80 to200 and a boiling point of over 150° C. at atmospheric pressure,preferably ethylene glycol di(meth) acrylate and/or tetrahydrofurfuryl(meth)acrylate;

(B) a photopolymerization initiator;

(C1) a polyester having a moiety of an aromatic diol (a1) represented bythe following general formula: ##STR2## wherein Ph represents1,4-phenylene group, R¹, R² and R³ each represents a hydrogen atom ormethyl group, m and n each represents an integer of 1 to 15, and (m+n)is equal to 2 to 20; and

(C2) a phosphate represented by the general formula:

     R(OCH.sub.2 CH.sub.2).sub.S O!.sub.t PO(OH).sub.(3-t)     ( 2)

wherein R represents a alkyl group containing 5 to 16 carbon atoms, srepresents an integer of 1 to 4, and t represents 1 or 2.

2a! Fresnel lens

A Fresnel lens comprising a resin formed by UV cure of composition 1a!in situ on a sheet or plate made of a methyl methacrylate (co)polymer.

2b! Fresnel lens

A Fresnel lens comprising a resin formed by UV cure of composition 1b!in situ on a sheet or plate made of a methyl methacrylate (co)polymer.

3a! Rear projection screen

A rear projection screen comprising a Fresnel lens sheet or Fresnel lensplate carrying the Fresnel lens 2a! as disposed on a sheet or plate madeof a methyl methacrylate (co)polymer.

3b! Rear projection screen

A rear projection screen comprising a Fresnel lens sheet or Fresnel lensplate carrying the Fresnel lens 2b! as disposed on a sheet or plate madeof a methyl methacrylate (co)polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing one example of a rear projectionscreen. In FIG. 1, the reference numeral 1 stands for a rear projectionscreen, 2 for a Fresnel lens sheet or Fresnel lens plate, 3 for alenticular lens sheet, 4 for a light absorbing layer, 5 for a Fresnellens, and 6 for a sheet or plate made of a methyl methacrylate (co)polymer.

DETAILED DESCRIPTION OF THE INVENTION

Each of the compositions 1a! and 1b! of the present invention is aUV-curable resin composition for use in the formation of a Fresnel lenson a sheet or plate made of a methyl methacrylate (co)polymer, namely ahomopolymer of methyl methacrylate or a copolymer of methyl methacrylatewith one or more other (meth)acrylates.

The composition 1a! is a UV-curable resin composition of the urethanegroup-containing (meth)acrylate type and the composition 1b! is aUV-curable resin composition of the (meth)acrylate type which is furthersupplemented with a polyester (C1) and a phosphate (C2). With either ofthese compositions, the resin formed by UV radiation cure is a(meth)acrylate resin.

The urethane group-containing (meth)acrylate (A2) in the composition 1a!of the invention and the polyester (C1) in the composition 1b! arecomparable in that they share a moiety of an aromatic diol (a1) incommon.

The aromatic diol (a1) is an addition product of a bisphenol withalkylene oxide as can be seen from the above general formula (1).

The bisphenol mentioned above includes such species as bisphenol A,bisphenol F, and bisphenol AD.

The alkylene oxide includes such species as ethylene oxide (briefly,EO), propylene oxide (briefly, PO) and these may be used in combinationto give an EO-PO random addition product or an EO-PO block additionproduct.

Each of m and n in general formula (1), both representing the number ofmoles of alkylene oxide added, is an integer of usually 1 to 15 andpreferably 1 to 7, and (m+n) is usually 2 to 20 and preferably 2 to 12.If (m+n) is within said range, the scratch resistance of the lensavailable on cure of the composition will be good and the refractiveindex of the cured composition will be high.

The addition product of the bisphenol with alkylene oxide can beproduced typically by a known process such as a prosess that EO and/orPO are added to a bisphenol by addition reaction in the presence of abasic catalyst.

The composition 1a! of the present invention comprises, as mentionedabove, a (meth)acrylate containing hydroxyl group and aromatic ring(A1), a urethane group-containing (meth)acrylate (A2), an aromaticring-containing (meth)acrylate (A3), and a photopolymerization initiator(B) as essential components.

The (meth)acrylate containing hydroxyl group and aromatic ring (A1)includes but is not limited to

(A11) 2-hydroxy-3-phenoxypropyl (meth)acrylate,

(A12) 2-hydroxy-3-(2'-, 3'-, or 4'-methylphenoxy)propyl (meth)acrylate,

(A13) (meth)acryloyloxyethyl (meth)acryloyloxy-2-hydroxypropylphthalate, and

(A14) the addition product of a bisphenol (e.g. bisphenol A, bisphenolF, or bisphenol S) glycidyl ether with a (meth)acrylate.

Preferred among them are said (A11) and said (A12), both of which havelow viscosity values.

The urethane group-containing (meth)acrylate (A2) includes but is notlimited to

(A21) the reaction product of an organic polyisocyanate (b2) with ahydroxyl group-containing (meth)acrylate (b3) and an aromatic diol (a1),

(A22) the reaction product of (b2) with (b3) and a polyester polyol (b1)derived from (a1) and a dicarboxylic acid (a2),

(A23) the reaction product of (b2) with (b3) and the combination of (a1)and (b1).

Preferred among them is (A22).

The dicarboxylic acid (a2) includes but is not limited to maleic acid,fumaric acid, succinic acid, adipic acid, phthalic acid, isophthalicacid, terephthalic acid, and acid anhydrides thereof. Preferred amongthem are maleic acid, fumaric acid, succinic acid and adipic acid.

The polyester polyol (b1) can be obtained from an aromatic diol (a1) anda dicarboxylic acid (a2) under the known esterification conditions. TheOH/COOH equivalent ratio for the production of the polyester polyol (b1)is generally 2.0 to 1.05 and preferably 2.0 to 1.5.

The diol as a constituent of a urethane group-containing (meth)acrylate(A2) is said (a1) and/or said (b1) but where necessary a third diol canbe used in conjunction. The third diol is preferably one having amolecular weight of not more than 400. The use of a diol with amolecular weight of more than 400 is undesirable, since the refractiveindex will be seriously decreased.

The third diol includes but is not limited to ethylene glycol, propyleneglycol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,4-butanediol,1,6-hexanediol, polyethylene glycol (degree of polymerization: 2 to 9),polypropylene glycol (degree of polymerization: 2 to 6), andpolycaprolactonediol (degree of polymerization: 2 or 3).

The proportion of the third diol, if used, is generally not more than 30weight % and preferably not more than 10 weight %, based on the weightof (a1).

The organic polyisocyanate (b2) as a constituent of said urethanegroup-containing (meth)acrylate (A2) includes but is not limited to

(b21) 2,4-tolylene diisocyanate,

(b22) 2,6-tolylene diisocyanate,

(b23) xylylene diisocyanate,

(b24) 4,4'-diphenylmethane diisocyanate,

(b25) isophorone diisocyanate,

(b26) dicyclohexylmethane diisocyanate,

(b27) hexamethylene diisocyanate, and

(b28) the modification products thereof (e.g. carbodiimides,urethodiones, biurets, isocyanurates, etc.). In addition, optionalcombinations of the above compounds can also be mentioned.

Preferred, among them, are (b21), (b22), (b23) and (b24) andcombinations of two or more of them.

The hydroxyl-containing (meth)acrylate (b3) as a constituent of saidurethane group-containing (meth)acrylate

(A2) includes but is not limited to

(b31) 2-hydroxyethyl (meth)acrylate,

(b32) 2-hydroxypropyl (meth)acrylate,

(b33) 4-hydroxybutyl (meth)acrylate,

(b34) 2-hydroxy-3-butoxypropyl (meth)acrylate, and

(b35) 2-hydroxy-3-phenoxypropyl (meth)acrylate.

Preferred, among them, are (b31) and (b32).

There is no particular limitation on production method for said (A2) buta typical process comprises reacting said (a1) and/or said (b1) withsaid (b2) in the known manner for urethane-forming reaction and, then,reacting with (b3).

The number average molecular weight of a urethane group-containing(meth)acrylate (A2) is generally 2,000 to 10,000 and preferably 3,000 to8,000. If the number average molecular weight is within the range of2,000 to 10,000, sufficient flexibility will be obtained and theviscosity of the resin composition will be sutable for not causing airentrapment to ensuring the lens functions.

The refractive index (25° C.) of said (A2) is generally not less than1.52 and preferably not less than 1.53.

The aromatic ring-containing monofunctional (meth)acrylate (A3) includesbut is not limited to

(A31) phenyl (meth)acrylate,

(A32) benzyl (meth)acrylate,

(A33) a (meth)acrylate of addition product of phenol with EO and/or PO(number of moles of EO and/or PO added: 1 to 6),

(A34) a (meth)acrylate of addition product of nonylphenol with EO and/orPO (number of moles of EO and/or PO added: 1 to 6), and

(A35) a (meth)acrylate of addition product of dodecylphenol with EOand/or PO (number of moles of EO and/or PO added: 1 to 6).

Preferred, among them, are (A33), (A34) and a combination thereof.

The composition 1a! of the present invention may contain 20 to 60 weight% of said (A1) and preferably 30 to 50 weight %, 10 to 50 weight % ofsaid (A2) and preferably 20 to 40 weight %, and 5 to 50 weight % of said(A3) and preferably 10 to 40 weight %.

Using said (A1) in a proportion of 20 to 60 weight % may be attainableof satisfactory adhesion to a sheet or plate and of the viscositysuitable for preventing air entrapment in moulding to make sure of thelens functions.

Using said (A2) in a proportion of 10 to 50 weight % may be attainableof flexibility and scratch resistance and also of the viscosity suitablefor preventing air entrapment in moulding to make sure of the lensfunctions.

Using said (A3) in a proportion of 5 to 50 weight % will ensure suitableviscosity and adhesion to a sheet or plate.

In the composition 1a! of the present invention, the urethanegroup-containing (meth)acrylate (A2) as it is alone shows antistaticproperties, but there are cases that (A2) alone ensures only inadequateantistatic properties. In order to realize sufficient antistaticproperties with (A2) alone, it must be incorporated in an increasedproportion but it occasionally causes deterioration of adhesion.

In such cases, where necessary, the antistatic properties can beimproved by using a phosphate (C2) of the following general formula (2)in combination with said (A2), whereby the objective performance can beobtained. This phosphate (C2) contributes to improve scratch resistanceof the cured composition and, at the same time, functions as a moldrelease agent

     R(OCH.sub.2 CH.sub.2).sub.S O!.sub.t PO(OH).sub.(3-t)     (2)

wherein R represents alkyl group containing 5 to 16 carbon atoms, srepresents an integer of 1 to 4, t represents an integer of 1 or 2.

Referring to general formula (2), R is an alkyl group containing 5 to 16carbon atoms. With R inside the above carbon number range, sufficientantistatic performance can be obtained.

The symbol s stands for an integer of 1 to 4. If s is equal to zero, thephosphate (C2) will be insoluble in the composition of the invention or,even if soluble, will tend to separate out during storage. If the valueof s is 5 or more, the required antistatic properties will not be fullyexpressed.

The symbol t represents an integer of 1 or 2. If t is equal to zero,said (C2) will remain insoluble in the composition 1a! of the invention.If t is equal to 3, antistatic properties will not be fully expressed.

The phosphate (C2) can be obtained by adding EO to an aliphatic alcoholof 5 to 16 carbon atoms in a known manner and reacting the additionproduct further with either phosphoric acid or a derivative thereof(e.g. diphosphorus pentaoxide).

The aliphatic alcohol of 5 to 16 carbon atoms mentioned above is astraight-chain monohydric alcohol or a branched monohydric alcohol,which includes n-hexyl alcohol, n-octyl alcohol, 2-ethylhexyl alcoholand n-lauryl alcohol, to mention just a few preferred species.

The proportion of the phosphate (C2), when used, in the composition 1a!of the present invention is preferably 0.1 to 2.0 weight % and morepreferably 0.3 to 1.5 weight %. In using the proportion of 0.1 to 2.0weight % of (C2), appreciable antistatic properties and adhesion to asheet or plate will be insured.

For improving adhesion further, among other purposes, a plasticizer (C3)with a solubility parameter in the range of 10.0 to 11.5 may beoptionally incorporated in the composition 1a! of the present invention.

The solubility parameter (briefly, SP) of plasticizer (C3) is 10.0 to11.5 and preferably 10.5 to 11.2. SP value of (C3) within the aboverange will realize improvement in adhesion. The SP values mentioned inthis specification are the values calculated in accordance with PolymerEngineering and Science,14 (2), 147 (1974).

The plasticizer (C3) includes but is not limited to the followingspecies.

    ______________________________________                                        · Dimethyl phthalate                                                                        (SP 10.90)                                             · Diethyl phthalate                                                                         (SP 10.54)                                             · Dibutyl phthalate                                                                         (SP 10.07)                                             · Butyl benzyl phthalate                                                                    (SP 10.74)                                             · Dicyclohexyl phthalate                                                                    (SP 10.39)                                             · Ethyl phthalyl ethyl glycolate                                                            (SP 10.75)                                             · Butyl phthalyl butyl glycolate                                                            (SP 10.17)                                             · Triphenyl phosphate                                                                       (SP 10.73)                                             · Tricresyl phosphate                                                                       (SP 10.46)                                             · Diphenyl cresyl phosphate                                                                 (SP 10.54)                                             · Polyethylene glycol dibenzoate (degree of                                                 (SP 11.15 to 10.02)                                    polymerization of ethylene glycol; 1 to 12)                                   · Polypropylene glycol dibenzoate (degree of                                                (SP 10.89 to 10.04)                                    polymerization of propylene glycol; 1 to 4)                                   ______________________________________                                    

Preferred, among them, are species with high refractive indices such asdimethyl phthalate, butyl benzyl phthalate, triphenyl phosphate,tricresyl phosphate and diphenyl cresyl phosphate.

The proportion of plasticizer (C3), if used, in the composition 1a! ofthe present invention is 1 to 20 weight % and preferably 3 to 15 weight%. In using the (C3) in the proportion of 1 to 20 weight %, sufficientimprovement can be obtained in adhesion to a sheet or plate and thehardness of the cured composition will be sufficient to provide the lenswith dimensional stability.

In the composition 1a! of the present invention, one or more(meth)acrylate monomers other than said (A1), said (A2), and said (A3)can be employed where necessary.

The other (meth)acrylate monomers mentioned above may, for example, bethe following species.

Tetrahydrofurfuryl (meth)acrylate

Methoxyethyl (meth)acrylate

Ethoxyethyl (meth)acrylate

Butoxyethyl (meth)acrylate

Glycidyl (meth)acrylate

Isobornyl (meth)acrylate

2-Hydroxyethyl (meth)acrylate

2-Hydroxypropyl (meth)acrylate

4-Hydroxybutyl (meth)acrylate

2-Hydroxy-3-butoxypropyl (meth)acrylate

Ethylene glycol di(meth)acrylate

1,2- or 1,3-Propylene glycol di(meth)acrylate

Diethylene glycol di(meth)acrylate

1,6-Hexanediol di(meth)acrylate

Neopentyl glycol di(meth)acrylate

Di(meth)acrylate of a bisphenol (e.g. bisphenol A, bisphenol F, orbisphenol S) or di(meth)acrylate of the addition product of thebisphenol with alkylene oxide

Trimethylolpropane tri(meth)acrylate

Pentaerythritol tetra(meth)acrylate

Dipentaerythritol hexa(meth)acrylate

Alkylene oxide-modified trimethylolpropane tri(meth) acrylate

Alkylene oxide-modified pentaerythritol tetra(meth) acrylate

Alkylene oxide-modified dipentaerythritol hexa(meth) acrylate

The proportion of such other (meth)acrylate monomer or monomers to thetotal weight of (A1), (A2) and (A3) combined is usually not more than 30weight % and preferably not more than 20 weight %.

The photopolymerization initiator (B) as an essential component of bothcompositions 1a! and 1b! of the present invention includes but is notlimited to benzoin alkyl ethers, benzyl dimethyl ketal,

1-hydroxycyclohexylphenylketone,

2-hydroxy-2-methyl-1-phenylpropane-1-one, benzophenone, methylbenzoylformate, isopropylthioxanthone. These may be in combination used.

The proportion of the photopolymerization initiator (B) is usually 0.1to 10 weight % and preferably 0.5 to 6 weight %, based on the totalcomposition weight for each of compositions 1a! and 1b!.

Where necessary, a thermal polymerization inhibitor, antifoaming agent,leveling agent, coupling agent, antistatic agent, ultraviolet absorber,and other known additives can be selectively incorporated in each ofcompositions 1a! and 1b!.

The composition 1b! of the present invention contains said polyester(C1) and said phosphate (C2) in addition to said components (A1) and(A4) as well as said photopolymerization initiator (B).

Among the above components, said (A1) and said (B) as essentialcomponents are also contained in composition 1a! of the invention, whilethe phosphate (C2) is an optional component of composition 1a!, andthese components are as described hereinbefore.

The species and preferred species of each of (A1), (B), and (C2) incomposition 1b! of the invention are the same as those in composition1a!.

The mono- or di(meth)acrylate monomer (A4) has a molecular weight of 80to 200 and a boiling point of over 150° C. at atmospheric pressure. Ifthe molecular weight is less than 80, the working environment will beadversely affected by the dermal irritancy and intense odor. On theother hand, if the molecular weight exceeds 200, adhesion of thecomposition to a sheet or plate made of a methyl methacrylate(co)polymer will be adversely affected. If the boiling point is equal toor below 150° C., its high volatility will interfere with the productionof products of stable performance.

The mono- or di(meth)acrylate monomer (A4) includes but is not limitedto

(A41) phenoxy ethylene glycol acrylate,

(A42) tetrahydrofurfuryl (meth)acrylate,

(A43) methoxyethyl (meth)acrylate,

(A44) ethoxyethyl (meth)acrylate,

(A45) butoxyethyl (meth)acrylate,

(A46) glycidyl (meth)acrylate,

(A47) 2-hydroxyethyl (meth)acrylate,

(A48) diethylene glycol (meth)acrylate,

(A49) 1,2- or 1,3-propylene glycol diacrylate.

Preferred, among them, are (A42), (A48), and a combination thereof.

In the composition 1b! of the present invention, said (meth)acrylate(A1) and said mono- or di(meth)acrylate monomer (A4) are components forimproved adhesion to a sheet or plate made of a methyl methacrylate(co)polymer.

The polyester (C1) mentioned above has a moiety of an aromatic diol (a1)represented by the general formula (1) and can be obtained byesterification reaction between diol compound comprising said aromaticdiol (a1) and the dicarboxylic acid (a2).

As the diol for a diol moiety of (C1), one or more other diols can beused in combination with (a1) where necessary. The other diols that canbe used are preferably diols having molecular weights less than 400. Useof a diol with a molecular weight in excess of 400 results in a markeddecrease in refractive index.

Such other diol includes but is not limited to ethylene glycol,propylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol,1,4-butanediol, 1,6-hexanediol, polyethylene glycol (degree ofpolymerization; 2 to 9), polypropylene glycol (degree of polymerization;2 to 6), polycaprolactonediol (degree of polymerization; 2 or 3).

The other diol or diols can be used in a proportion of usually not morethan 30 weight % and preferably not more than 20 weight %, relative to(a1).

The dicarboxylic acid (a2) as a constituent of said polyester (C1) arethe same as those in composition 1a!, preferably, among them, arespecies having highly refractive indices such as maleic acid, fumaricacid, phthalic acid, isophthalic acid, terephthalic acid, acid anhydridethereof and combinations of two or more of them.

The number average molecular weight of said polyester (C1) is usually5,000 to 60,000 and preferably 7,000 to 40,000. If the number averagemolecular weight of (C1) is within the range of 5,000 to 60,000, thecomposition will not retain tackiness after UV cure and the viscosity ofthe composition will not be increased so much that the problem that theresidual air cells in the molding will interfere with lens functionswill not occur.

The polyester (C1) can be produced by the known esterification reaction.The OH/COOH equivalent ratio for use in the production of (C2) isusually 1.3 to 0.7 and preferably 1.2 to 0.8.

The proportions of said (A1), said (A4), and said polyester (C1) in thecomposition 1b! of the present invention may be 10 to 50 weight % of(A1) and preferably 15 to 30 weight %, 10 to 50 weight % of (A4) andpreferably 15 to 40 weight %, and 10 to 40 weight % of (C1) andpreferably 15 to 35 weight %.

If the proportion of (A1) is within the range of 10 to 50 weight %,adhesion to a sheet or plate made of a methyl methacrylate (co)polymerwill be adequate and the viscosity of the system will be good forworkability.

If the proportion of (A4) is within the range of 10 to 50 weight %,adhesion to a sheet or plate made of a methyl methacrylate (co)polymerwill be adequate and the refractive index of the lens will not bedecreased and the viscosity of the system will be good for workability.

If the proportion of (C1) is within the range of 10 to 40 weight %,desired antistatic properties will be obtained and the viscosity willnot be increased so much as to cause formation of air cells in themolding and interference with lens functions.

The composition 1b! of the present invention contains said phosphate(C2) in addition to said polyester (C1) as an essential component. Eachof components (C1) and (C2) has its own antistatic properties. However,with (C1) alone, it must be used in a large proportion in order toobtain an adequate degree of antistaticity and this practice wouldadversely affect adhesion. On the other hand, (C2) alone would notprovide for a sufficient antistatic effect. Thus, the use of (C1) and(C2) in combination results in improved antistatic properties tocontribute to the desired performance. Furthermore, (C2) not onlycontributes to improved scratch resistance of the cured composition butfunctions as a mold release agent.

The proportion of said phosphate (C2) in the composition 1b! of thepresent invention is usually 0.1 to 2 weight % and preferably 0.3 to 1.5weight %. If the proportion is within the range of 0.1 to 2 weight %,(C2) adequately contributes to antistatic properties and has adequateadhesion to the substrate.

In addition to said (A1) and said (A4) as essential components, thecomposition 1b! of the present invention may contain one or more other(meth)acrylate monomers. The other (meth)acrylate monomer that can beused includes but is not limited to the followings.

Nonylphenoxy diethylene glycol (meth)acrylate

Dodecylphenoxy diethylene glycol (meth)acrylate

Diethylene glycol di(meth)acrylate

1,6-Hexanediol di(meth)acrylate

Neopentyl glycol di(meth)acrylate

Bisphenol (e.g. bisphenol A, bisphenol F, bisphenol S) ordi(meth)acrylate of the addition product of bisphenol with alkyleneoxide

Trimethylolpropane di- or tri(meth)acrylate

Pentaerythritol tri- or tetra(meth)acrylate

Dipentaerythritol tri-, tetra-, penta-, or hexa(meth) acrylate

Alkylene oxide-modified trimethylolpropane tri(meth) acrylate

Alkylene oxide-modified pentaerythritol tetra(meth) acrylate

Alkylene oxide-modified dipentaerythritol hexa(meth) acrylate

The viscosity of the composition 1a! or 1b! according to the presentinvention is preferably 500 to 5,000 cps at the casting temperature. Ifthe viscosity on casting is within the above range, air cells will notbe entrapped in the molding and hence will not impair less functions.

The refractive indices (25° C.) of the cured resins from thecompositions 1a! and 1b! of the present invention is usually not lessthan 1.54 and preferably not less than 1.55. Moreover, the surfaceresistivities of these cured resins are usually not more than 10¹³ Ω andpreferably not more than 10¹² Ω. Since the compositions 1a! and 1b! ofthe present invention can thus be tailored to yield cured resins withrefractive indices not less than 1.54, sufficiently short focal lengthscan be realized when they are applied to the manufacture of Fresnellens. Moreover, because the compositions have been provided withantistatic properties, no static electricity is generated in theassembling of a lens sheet or a lens plate so that improved handlingworkability can be expected with no deposits of dust.

Each of the compositions 1a! and 1b! of the present invention can becured by UV irradiation. There is no particular limitation on the typeof UV irradiation equipment but a high-pressure mercury lamp or a metalhalide lamp can be used as a radiation source.

As shown in FIG. 1, the rear projection screen 1 of the inventioncomprises a sheet or plate 6 made of a methyl methacrylate (co)polymerand the Fresnel lens 5 formed by the UV curing of the composition 1a! or1b! of the invention in situ on the light emergence surface of saidsheet or plate 6, and a lenticular lens sheet 3 comprising lenticularlenses arranged on both incidence and emergence surfaces and havinglight absorbing layer 4 in the non-light-converging(non-light emerging)zones formed on the emergence surface as the projected light isconverged by the lenticular lenses on the incidence surface in such amanner that the Fresnel lens 5 is juxtaposed with the lenticular lenseson the incidence surface of lenticular lens sheet 3.

The Fresnel lens 5 is directly formed on the sheet or plate 6 by UV cureof said composition 1a! or 1b! without interposition of an adhesivelayer such as a primer layer on the sheet or plate 6.

The sheet or plate thus constitued by disposing thereon the Fresnel lensof the present invention may be refered to as the Fresnel lens sheet orFresnel lens plate in the specification.

The rear projection screen 1 of the present invention comprises theFresnel lens sheet or Fresnel lens plate 2 carrying the Fresnel lens 5formed by curing the composition 1a! or 1b! of the invention, and inaddition to the use in combination with the lenticular lens sheet 3 asillustrated in FIG. 1, it can be used in combination with various otheralternative screen lens sheets.

The sheet or plate 6 is made of a methyl methacrylate (co)polymer,namely, a homopolymer of methyl methacrylate or a copolymer of methylmethacrylate with one or more other alkyl (meth)acrylates the carbonnumber of the alkyl moiety of which are usually 1 to 18.

The methyl methacrylate content of said sheet or plate is usually notless than 70 weight % and preferably not less than 80 weight %. If theproportion of methyl methacrylate is within said range, adequateadhesion to the cured composition of the invention will be insured.

The sheet or plate 6 made of a methyl methacrylate (co)polymer can beformed by the known molding technique such as injection molding,extrusion molding, or casting.

The thickness of the sheet or plate may be ranged from 0.5 to 5 mm.

Production of the Fresnel lens sheet or Fresnel lens plate can becarried out typically by a process which comprises applying thecomposition 1a! or 1b! of the invention to a Fresnel lens mold,superimposing said sheet or plate on said composition under applicationof pressure to avoid entrapping of air, irradiating the assemblage withultraviolet light to cure the composition 1a! or 1b! followed byreleasing from the mold.

EXAMPLES

The following examples illustrate the present invention in furtherdetail and should by no means be construed as defining the scope of theinvention. In the examples, all parts are by weight.

Examples of Synthesis 1 to 3

Using the components (a1), (a2), (b2) and (b3) according to the formulas(weight ratios) indicated in Table 1, urethane group-containing acrylate(A2-1 to A2-3) were produced by the following method. The refractiveindex (25° C.) of each sheet was determined with an Abbe refractometer(manufactured by Atago). The results are shown in Table 1.

Synthetic process

A four-necked flask equipped with a stirrer, condensor and thermometerwas charged with the indicated amounts of (a1) and (a2) and 0.025 partof dibutyltin oxide and the dehydrative esterification reaction wascarried out at 10 mmHg and 200° C. for 8 hours. To the resultingpolyester (b1) was added the indicated amount of (b2) and the reactionwas further carried out at 80° to 90° C. for 2 hours. Then, theindicated amount of (b3) was added and the reaction was further carriedout at 80° to 90° C. for 3 hours. In this manner, urethanegroup-containing acrylates (A2-1 to A2-3) were synthesized.

                  TABLE 1                                                         ______________________________________                                        Example of                                                                    Synthesis                                                                              1           2           3                                            ______________________________________                                        Symbol   A2-1        A2-2        A2-3                                         a1       Bisphenol A EO                                                                            Bisphenol A EO                                                                            Bisphenol A EO                                        (10 mol)    (6 mol)     (4 mol)                                               addition    addition    addition                                              product     product     product                                      Amount of a1                                                                           401         400         400                                          a2       Maleic      Succinic acid                                                                             Succinic acid                                         anhydride                                                            Amount of a2                                                                           29.4        48.0        72.8                                         b2       Xylylene    Tolylene    Tolylene                                              diisocyanate                                                                              diisocyanate                                                                              diisocyanate                                 Amount of b2                                                                           69.2        86.0        79.0                                         b3       Hydroxyethyl                                                                              Hydroxyethyl                                                                              Hydroxyethyl                                          acrylate    acrylate    acrylate                                     Amount of b3                                                                           15.8        21.0        33.8                                         Number   7,480       6,120       4,050                                        average mol.                                                                  wt.                                                                           Refractive                                                                             1.546       1.537       1.550                                        index (25° C.)                                                         ______________________________________                                    

In the table, BO stands for ethylene oxide and PO for propylene oxide.

Comparative Examples of Synthesis 1 and 2

Using the diol, (b2), and (b3) in accordance with the formulas (weightratios) shown in Table 2, control urethane group-containing acrylates(UA-1 and UA-2) were synthesized by the following comparative method ofsynthesis. The refractive index (25° C.) of each urethanegroup-containing acrylate synthesized is shown in Table 2.

Comparative method of synthesis

The same reactor as used for the above-described method of synthesis wascharged with the indicated amounts of diol and (b2) and the reaction wascarried out at 80° to 90° C. for 2 hours. Then, the indicated amount of(b3) was added and the reaction was further carried out at 80° to 90° C.for 3 hours. In this manner, urethane group-containing acrylates (UA-1and UA-2) were obtained.

                  TABLE 2                                                         ______________________________________                                        Comparative Example                                                           of Systhesis  1           2                                                   ______________________________________                                        Symbol        UA-1        UA-2                                                Diol          Bisphenol A EO                                                                            Polycaprolactone-                                                 (40 mol)    diol (Mw = 2,000)                                                 addition product                                                Amount of diol                                                                              398         400                                                 b2            Tolylene    Isophorone                                                        diisocyanate                                                                              diisocyanate                                        Amount of b2  51.2        44.4                                                b3            Hydroxyethyl                                                                              Hydroxyethyl                                                      acrylate    acrylate                                            Amount of b3  21.9        46.4                                                Number average                                                                              4,995       2,676                                               mol. wt.                                                                      Refractive    1.517       1.484                                               index (25° C.)                                                         ______________________________________                                    

Examples 1 to 5

According to the formulas (weight ratios) shown in Table 3, resincompositions 1a! of the invention (Examples 1 to 5) were prepared. Theviscosity of each sample at 35° C. was measured with a BL viscosimeter(manufactured by Tokyo Keiki). In addition, 50 μm films were preparedand irradiated with 1000 mJ/cm² of ultraviolet light to provide curedfilms and the refractive index of each film at 25° C. was determined.The viscosity (35° C.) and refractive index of each film are shown inTable 4.

Comparative Examples 1 to 3

According to the formulas (weight ratios) shown in Table 3, comparativeresin compositions (Comparative Examples 1 to 3) were prepared. Theviscosity (35° C.) and refractive index of each cured composition areshown in Table 4.

Test Example 1

Using the resin compositions of Examples 1 to 5 and Comparative Examples1 to 3, Fresnel lenses were prepared by the following test method andtested for adhesion to a sheet, mold releasability, and scratchresistance. The results are shown in Table 4.

Test method

Each of the UV-curable resin compositions shown in Table 3 was applied,in a thickness of 50 to 150 μm, onto a chrome-plated Fresnel lens mold(50 cm×50 cm) by the dispenser controlled at 35° C., and a 2 mm-thicksheet made of a methyl methacrylate copolymer (Sumipex HT(trade name),manufactured by Sumitomo Chemical) was superimposed on the dispensedresin composition in the mold under application of pressure with careexercised to avoid air entrapment. Then, using a high-pressure mercurylamp, the UV-curable resin was cured by 1,000 mJ/cm² of UV light and themold was then released to provide a Fresnel lens.

The mold releasability and the performance parameters of each Fresnellens were evaluated as follows.

(1) Mold releasability: The ease of release from the mold in theproduction of the Fresnel lens

Criteria

∘: Easy to release

×: Difficult to release, with deformation ensuing

(2) Air entrapment: The presence or absence of air cells in the Fresnellens

Criteria

∘: no air cells

×: Air cells

(3) Adhesion: The degree of adhesion of the UV-cured resin compositionto the sheet

The sample is crosshatched with a knife at 1 mm/pitch (10×10) and acellophane tape was set in position and peeled off at an angle of 90degrees. The degree of exfoliation of the cured resin from the sheet wasevaluated.

Criteria

∘: not exfoliated

×: Exfoliated

(4) Scratch resistance: Scratchability of the Fresnel lens

Criteria

∘: Scratching with the finger nail leaves no mark

×: Scratching with the finger nail leaves a mark

                  TABLE 3                                                         ______________________________________                                                                 Comparative                                                     Example       Example                                                         1   2      3     4    5   1    2   3                               ______________________________________                                        A1  Aronix M-5700                                                                              50    50   45  30   30  10   50  50                          A2  A2-1         25                  30                                           A2-2               30                                                         A2-3                    40  40       40                                       UA-1                                      30                                  UA-2                                          30                          A3  Aronix M-101 15    20       20   35  50   10                                  Aronix M-111            15                    20                              NK Ester A-400                                                                             10                           10                                  Viscoat 195                 10    5                                       B   Darocur 1173  2     2    2   2    2   2    2   2                          ______________________________________                                    

In the table, each component means as follows;

Aronix M-5700: 2-Hydroxy-3-phenoxypropyl acrylate, (trade name)manufactured by Toagosei Chemical Industry Co. Ltd.

Aronix M-101: Phenoxy diethylene glycol acrylate, (trade name)manufactured by Toagosei Chemical Industry Co. Ltd.

Aronix M-111: Nonylphenoxy ethylene glycol acrylate, (trade name)manufactured by Toagosei Chemical Industry Co. Ltd.

NK Ester A-400: Polyethylene glycol diacrylate, (trade name)manufactured by Shin Nakamura Kagaku

Viscoat 195: 1,4-Butanediol diacrylate, (trade name) manufactured byOsaka Yuki Kagaku

Darocur 1173: 2-Hydroxy-2-methyl-1-phenylpropan-1-one, (trade name)manufactured by Ciba-Geigy

                  TABLE 4                                                         ______________________________________                                        Vis-       Re-              Air                                               cosity/    fractive                                                                              Release- entrap-                                                                             Ad-   Scratch                               cps        index   ability  ment  hesion                                                                              resistance                            ______________________________________                                        Example                                                                       1      3,200   1.552   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       2      3,660   1.550   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       3      4,800   1.553   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       4      3,400   1.551   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       5      3,800   1.550   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       Com-                                                                          parative                                                                      Example                                                                       1      2,500   1.549   ∘                                                                        ∘                                                                       x     ∘                       2      4,500   1.539   ∘                                                                        ∘                                                                       x     ∘                       3      2,800   1.521   x      x     x     x                                   ______________________________________                                    

Examples 6 to 10

In accordance with the formulas (weight ratios) shown in Table 5, resincompositions (1a) each containing a plasticizer (C3) according to theinvention (Examples 6 to 10) were prepared. The viscosity of each sampleat 35° C. was measured with a BL viscosimeter (manufactured by TokyoKeiki). In addition, 50 μm films were prepared and irradiated with 1000mJ/cm² of ultraviolet light to provide cured sample films and therefractive index of each film at 25° C. was determined. The viscosity(35° C.) and refractive index of each film are shown in Table 6.

Test Example 2

Using the resin compositions of Examples 6 to 10, Fresnel lenses wereprepared in accordance with the same test method as Test Example 1 andevaluated for adhesion to a sheet, mold releasability, and scratchresistance. The results are shown in Table 6.

                  TABLE 5                                                         ______________________________________                                                      Example                                                                       6      7     8       9   10                                     ______________________________________                                        A1     Aronix M-5700                                                                              50       40  30    40  40                                 A2     A2-1         30       35  40                                                  A2-2                            30  30                                        A2-3                                                                   A3     Aronix M-101 15       20        20  20                                        Aronix M-111              15                                           C3     Tricresyl phosphate                                                                         5        5  10         5                                        Dimethyl phthalate              10                                            NK Ester A-400             5                                                  Viscoat 195                          5                                 B      Darocur 1173  2        2   2     2   2                                 ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                               Vis-    Re-            Air                                                    cosity/ fractive                                                                              Release-                                                                             entrap-                                                                             Ad-   Scratch                             Example                                                                              cps     index   ability                                                                              ment  hesion                                                                              resistance                          ______________________________________                                        6      3,150   1.555   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       7      4,560   1.556   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       8      4,820   1.555   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       9      3,430   1.551   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       10     2,750   1.553   ∘                                                                        ∘                                                                       ∘                                                                       ∘                       ______________________________________                                    

Example of Synthesis 4

An autoclave equipped with a stirrer, condenser and thermometer wascharged with 558 parts of lauryl alcohol followed by addition of 264parts of ethylene oxide at 50° C. and the reaction was conducted at 200°C. for 2 hours. To the resulting alcohol (822 parts), 137 parts ofdiphosphorus pentaoxide was added and the reaction was further carriedout at 80° to 90° C. for 2 hours to provide a phosphate (C2-1).

Example of Synthesis 5

In the same autoclave as used in Example of Synthesis 4, 520 parts ofoctyl alcohol was reacted with 176 parts of ethylene oxide at 50° C.and, then, with 280 parts of diphosphorus pentaoxide to provide aphosphate (C2-2).

Comparative Example of Synthesis 3

A four-necked flask equipped with a stirrer, condensor and thermometerwas charged with 400 parts of lauric acid. After 300 parts oftriethanolamine was added at room temperature, the reaction was carriedout at room temperature for 2 hours to provide lauric acidtriethanolamine salt (LA-1).

Examples 11 to 15

According to the formulas (weight ratios) shown in Table 7, resincompositions 1a! (Examples 11 to 15) each containing a phosphate (C2)were prepared. The viscosity (35° C.) of each composition was measuredwith a BL viscosimeter (manufactured by Tokyo Keiki). In addition, 50μm-thick films were prepared and irradiated with ultraviolet light at1000 mJ/cm² to provide cured films and the refractive index (25° C.) ofeach cured film was determined. The viscosity (35° C.) and curedrefractive index values are shown in Table 8.

Test Example 3

Using the resin compositions of Examples 11 to 15, Fresnel lenses wereprepared by the same method as Test Example 1 and evaluated for adhesionto a sheet, mold releasability, and scratch resistance. The evaluationof antistatic properties was made by the following test method. Theresults are shown in Table 8.

Antistatic test

After conditioning to a temperature of 25° C. and a humidity of 60%, thesurface resistivity of each Fresnel lens was measured with Ultra HighResistance Meter (manufactured by Advantest).

                  TABLE 7                                                         ______________________________________                                                                 Comparative                                                  Example          Example                                                      11   12     13     14   15   1   2    3                               ______________________________________                                        A1  Aronix    50     40   30   40   40   50  40   40                              M-5700                                                                    A2  A2-1      30     30   40             30  30                                   A2-2                       30   35            30                              Aronix    20     30        20   25   20  20                                   M-101                                                                         Aronix                25                      30                              M-111                                                                         NK Ester              5                  10                                   A-400                                                                         Viscoat                    10                                                 195                                                                       C2  C2-1      0.3    0.5       0.5                                                C2-2                  0.5       1.0                                           LA-1                                     1.0  3.0                         B   Darocur   2      2    2    2    2    2   2    2                               1173                                                                      ______________________________________                                    

                                      TABLE 8                                     __________________________________________________________________________                                                Surface                                  Viscosity                                                                           Refractive                                                                          Release-                                                                            Air          Scratch                                                                             resistivity                              (cps) index ability                                                                             entrapment                                                                           Adhesion                                                                            resistance                                                                          (Ω)                         __________________________________________________________________________    Example                                                                       11     2,830 1.552 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       2.3 × 10.sup.10             12     2,330 1.553 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       3.5 × 10.sup.9              13     4,750 1.550 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       1.3 × 10.sup.9              14     3,400 1.553 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       4.3 × 10.sup.11             15     3,820 1.555 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       7.2 × 10.sup.9              Comparative                                                                   Example                                                                        1     2,760 1.553 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       6.4 × 10.sup.14              2     2,450 1.552 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       5.2 × 10.sup.14              3     2,940 1.551 ∘                                                                       ∘                                                                        x     ∘                                                                       7.8 × 10.sup.13             __________________________________________________________________________

Examples of Synthesis 6 and 7

Using the aromatic diol (a1) and dicarboxylic acid (a2) in accordancewith the formulas (weight ratios) shown in Table 9, polyesters (C1-1)and (C1-2) were synthesized by the following method of synthesis. Therefractive index (25° C.) of each polyester thus obtained was determinedwith an Abbe refractometer (manufactured by Atago). The results areshown in Table 9.

Method of synthesis

A four-necked flask equipped with a stirrer, condensor and thermometerwas charged with the indicated amounts of (a1) and (a2) as well as 0.025part of dibutyltin oxide and the dehydration esterification reaction wascarried out at 10 mmHg and 200° C. for 8 hours to provide polyesters(C1-1) and (C1-2).

                  TABLE 9                                                         ______________________________________                                                   Example of Synthesis                                                          6         7                                                        ______________________________________                                        Symbol       Polyester (C1-1)                                                                          Polyester (C1-2)                                     a1           Bisphenol A EO                                                                            Bisphenol F PO                                                    (10 mol)    (4 mol)                                                           addition product                                                                          addition product                                     Amount of a1 668         400                                                  a2           Terephthalic acid                                                                         Maleic anhydride                                     Amount of a2 144         98                                                   Number average                                                                             15,000      9,500                                                mol. wt.                                                                      Refractive   1.570       1.563                                                index (25° C.)                                                         ______________________________________                                    

Examples 16 to 20

According to the formulas (weight ratios) shown in Table 10, resincompositions 1b! of the invention (Examples 16 to 20) were prepared. Theviscosity (35° C.) of each composition prepared was measured with a BLviscosimeter (manufactured by Tokyo Keiki). In addition, 50 μm-thicksheets were prepared and irradiated with ultraviolet light at 1000mJ/cm² to give cured sheets and the refractive index (25° C.) of eachcured sheet was determined. The viscosity (35° C.) and cured refractiveindex (25° C.) values are shown in Table 11.

Comparative Examples 4 to 6

According to the formulas (weight ratios) shown in Table 10, comparativeresin compositions (Comparative Examples 4 to 6) were prepared. Theviscosity (35° C.) and cured refractive index (25° C.) values are shownin Table 11.

                  TABLE 10                                                        ______________________________________                                                                 Comparative                                                  Example          Example                                                      16   17     18     19   20   4   5    6                               ______________________________________                                        A1  Aronix    50     50   55   45   55   50  50   45                              M-5700                                                                    A4  Light Ester                                                                             20     25        15   15   20  25                                   EG                                                                            Light Ester           15   10                 20                              THF                                                                       C1  C1-1      30     25        30   20   30                                       C1-2                  25                 25   30                          C2  C2-1      0.3    0.5       0.5                                                C2-2                  0.5       1.0                                           LA-1                                     1.0  3.0                             Neomer                5         10            5                               BA641                                                                     B   Darocur   2      2    2    2    2    2   2    2                               1173                                                                      ______________________________________                                    

In the table, each component means as follows;

Light Ester: EG Ethylene glycol dimethacrylate, (trade name)manufactured by Kyoeisha Kagaku

Light Ester THF: Tetrahydrofurfuryl acrylate, (trade name) manufacturedby Kyoeisha Kagaku

Neomer BA641: Diacrylate of Bisphenol A-EO (4 mol) (trade name) addtionproduct, manufactured by Sanyo Chemical Industries, Ltd.

Test Example 4

Using the resin compositions of Examples 16 to 20 and ComparativeExamples 4 to 6, Fresnel lenses were prepared in accordance with thesame method as Test Example 1 and evaluated for adhesion to a sheet,mold releasability, and scratch resistance. The antistatic propertieswere also tested by the same procedure as described in Test Example 3.The results are shown in Table 11.

                                      TABLE 11                                    __________________________________________________________________________                                                Surface                                  Viscosity                                                                           Refractive                                                                          Release-                                                                            Air          Scratch                                                                             resistivity                              (cps) index ability                                                                             entrapment                                                                           Adhesion                                                                            resistance                                                                          (Ω)                         __________________________________________________________________________    Example                                                                       16     3,550 1.558 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       5.6 × 10.sup.9              17     2,230 1.553 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       1.3 × 10.sup.9              18     2,750 1.551 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       1.1 × 10.sup.9              19     3,220 1.550 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       6.5 × 10.sup.11             20     2,820 1.554 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       5.2 × 10.sup.9              Comparative                                                                   Example                                                                        4     2,660 1.551 ∘                                                                       ∘                                                                        ∘                                                                       ∘                                                                       4.7 × 10.sup.14              5     2,250 1.550 ∘                                                                       ∘                                                                        x     ∘                                                                       2.1 × 10.sup.14              6     2,840 1.552 ∘                                                                       ∘                                                                        x     ∘                                                                       5.4 × 10.sup.13             __________________________________________________________________________

The UV-curable Fresnel lens resin composition of the present inventionhas the following advantages.

1) Excellent adhesion to a sheet or plate made of a methyl methacrylatehomopolymer or a copolymer of methyl methacrylate with one or more other(meth)acrylates.

2) Easily moldable into Fresnel lens and other optical parts.

3) Providing a cured resin with a refractive index as high as 1.54 orhigher and excellent chemical resistance, toughness, heat resistance,and cold resistance.

4) The cured resin is highly antistatic.

Having the above-mentioned advantages, the composition of the presentinvention is of great utility value as a Fresnel lens material.

The rear projection screen of the present invention includes the Fresnellens sheet or Fresnel lens plate formed by curing the above UV-curableresin composition and, therefore, has an excellent Fresnel lens withhigh scratch resistance.

Therefore, there is no risk of damage or injury even on contact withother lens sheets during transport or assembly and it is no longernecessary to treat the surface by, for example, applying silicone oil orthe like between the Fresnel lens sheet or Fresnel lens plate and thelenticular lens sheet.

Furthermore, the rear projection screen of the present invention has ahighly antistatic Fresnel lens surface so that no deposit of dust occursin assembly, thus contributing to improved workability.

In addition, since the refractive index of the rear projection screen isas high as at least 1.54, it is possible to manufacture Fresnel lensesof short focal length to reduce the distance between the rear projectionscreen and the light source, thus permitting the design and manufactureof low-profile, compact projection television devices of large screensize.

We claim:
 1. A Fresnel lens comprising a resin formed by UV cure of aresin composition in situ on a sheet or plate made of a methylmethacrylate polymer or copolymer, wherein said resin compositioncomprises:(A1) an acrylate or methacrylate containing hydroxyl group andaromatic ring; (A2) a urethane group-containing acrylate or methacrylatehaving a moiety of an aromatic diol (a1) represented by the followinggeneral formula: ##STR3## wherein Ph represents 1,4-phenylene group R¹,R² and R³ each represents a hydrogen atom or methyl group, m and n eachrepresents an integer of 1 to 15, and (m+n) is equal to 2 to 20; (A3) anaromatic ring-containing monofunctional acrylate or methacrylate; (B) aphotopolymerization initiator; and (C3) a plasticizer with a solubilityparameter in the range of 10.0 to 11.5.
 2. The Fresnel lens according toclaim 1 which contains 20 to 60 weight % of (A1), 10 to 50 weight % of(A2), 5 to 50 weight % of (A3), 0.1 to 10 weight % of (B) and 1 to 20weight % of (C3).
 3. The Fresnel lens according to claim 1 wherein (A2)is a reaction product of an organic isocyanate (b2) with a hydroxylgroup-containing acrylate or methacrylate (b3) and a polyester polyol(b1) derived from (a1) and a dicarboxylic acid (a2).
 4. The Fresnel lensaccording to claim 3 wherein (a2) is at least one dicarboxylic acidselected from the group consisting of maleic acid, fumaric acid,succinic acid, adipic acid and the acid anhydrides thereof.
 5. TheFresnel lens according to claim 1 wherein (A1) is an acrylate containinghydroxyl group and aromatic ring; R² and R³ in formula (1) eachrepresent methyl; and a dicarboxylic acid (a2) being maleic acid orfumaric acid.
 6. The Fresnel lens according to claim 5 wherein R¹ informula (1) is a methyl group, and said dicarboxylic acid (a2) is maleicacid.
 7. A Fresnel lens comprising a resin formed by UV cure of a resincomposition in situ on a sheet or plate made of a methyl methacrylatepolymer or copolymer, wherein said resin composition comprises:(A1) anacrylate or methacrylate containing hydroxyl group and aromatic ring;(A2) a urethane group-containing acrylate or methacrylate having amoiety of an aromatic diol (a1) represented by the following generalformula: ##STR4## wherein Ph represents 1,4-phenylene group, R¹, R² andR³ each represents a hydrogen atom or methyl group, m and n eachrepresents an integer of 1 to 15, and (m+n) is equal to 2 to 20; (A3) anaromatic ring-containing monofunctional acrylate or methacrylate; (B), aphotopolymerization initiator; and (C2) a phosphate of the followinggeneral formula (2):

     R(OCH.sub.2 CH.sub.2).sub.S O!.sub.t PO(OH).sub.(3-t)     ( 2)

wherein R represents an alkyl group containing 5 to 16 carbon atoms, srepresents an integer of 1 to 4, and t represents an integer of 1 or 2.8. The Fresnel lens according to claim 7 which contains 20-50 weight %of (A1) 10 to 50 weight % of (A2), 5 to 50 weight % of (A3), 0.1 to 10weight % of (B) and 0.1 to 2.0 weight % of (C2).
 9. The Fresnel lensaccording to claim 7 wherein (A2) is a reaction product or an organicisocyanate (b2) with a hydroxyl group-containing acrylate ormethacrylate (b3) and a polyester polyol (b1) derived from (a1) and adicarboxylic acid (a2).
 10. The Fresnel lens according to claim 9wherein (a2) is at least one dicarboxylic acid selected from the groupconsisting of maleic acid, fumaric acid, succinic acid, adipic acid andthe acid anhydrides thereof.
 11. The Fresnel lens according to claim 7wherein (A1) is an acrylate containing hydroxyl group and aromatic ring;R² and R³ in formula (1) each represents methyl; and a dicarboxylic acid(a2) being maleic acid or fumaric acid.
 12. The Fresnel lens accordingto claim 11 wherein R¹ in formula (1) is a methyl group, and saiddicarboxylic acid (a2) is maleic acid.